Interfacially-polymerized (IF) membranes which consist of a very thin, dense film are typically coated on a thick porous substrate and are used extensively in the reverse-osmosis desalination of brine. The technology for the formation of economically feasible IF membranes for reverse osmosis was developed by Cadotte et al. and continues to be improved. (Cadotte, J. E., R. S. King, R. J. Majerle, and R. J. Petersen, "Interfacial synthesis in the preparation of reverse osmosis membranes," J. Macromol. Sci.-Chem. A15, 727, 1981)
IF membranes made with siloxanes, alkoxsilyls, or aryloxysilylys have been employed in the separation of gaseous mixtures. (U.S. Pat. No. 4,781,733 "Semipermeable Thin-Film Membranes Comprising Siloxane, Alkoxsilyl, and Aryloxysilyl Oligimers and Copolymers," Bend Research, Inc. Nov. 1, 1989)
IF membranes have also been used to form microcapsules for the controlled release of active ingredients. Several patents have been issued in this area over the past 25 years. A partial list of patented IF microcapsule processes and/or formulations is included in Table 1. Typically these IF microcapsules have been used to facilitate controlled-release pesticide formulations, releasing encapsulated active ingredient by diffusion through the microcapsule walls or by the rupture of the microcapsules.
While the literature is replete with description of tablets, capsules, and multiparticulates which deliver active substances by diffusion or osmotic pumping, none have taught the use of delivering active substances from tablets, capsules, or multiparticulates coated with an IF membrane.